scope:

This Standard specifies a method for testing ducted fans to determine the sound power radiated into an anechoically-terminated duct on the inlet and/or outlet side of the equipment. It applies to fans which emit steady, broadband, narrow-band and discrete-frequency sound. It applies to air temperatures between -50° C and +70°C. The test duct diameter range is from 0,15 m to 2 m. The maximum flow velocity is 30 m/s and the maximum swirl angle is 15° . An example of a method for determining the angle of swirl is given in annex F. The one-third octave band centre frequency range is from 50 Hz to 10000 Hz. The method applies to a sound source in which a fan is usually connected to ducts on at least one side. Examples of the ducted fans and fan equipment covered by this Standard are - ducted centrifugal fans; -ducted axial flow fans; - ducted mixed flow fans. This standard may also apply to other aerodynamic sound sources, such as boxes, dampers and throttle devices. This standard does not apply to non-ducted fans or non-ducted fan equipment.